Multidrug Resistance 1 (MDR1)


Inheritance: Autosomal incomplete dominant. This means that dogs with one or two copies of the mutation are at risk.

Symptoms: Dogs treated with the problem drugs are at risk of developing neurological symptoms. These include tremours, excess salivation, anorexia, blindness due to coma and death. Drugs can be lethal at low doses.

Description: Dogs affected by the MDR1 mutation are predisposed to adverse drug reactions caused by some classes of drugs (problem drug link to Univ of Washington page) which include ivermectin as well as some gastroprotectant and anti-cancer medications. These include acepromazine, butorphanol, doxorubicin, emodepside, erythromycin, ivermectin, loperamide, milbemycin, moxidectin, rifampin, selamectin, vinblastine and vincristine. You should notify your vet if your dog is at risk for MDR1 prior to the administration of any medications.